The one thing I really wanted for this story was a photograph of a mass mating of misfit leaf frogs, relatives of red-eyed tree frogs. Most other species mate whenever it rains. But these guys do so-called big-bang matings only twice a year, always following a significant rain.

The day the rain finally started, it kept raining—buckets and buckets of rain. Around 10 p.m. it slowed a little, so we went down to the swamp.

In the middle of the swamp are four or five trees, covered with a certain type of moss that these frogs lay their eggs in. There were thousands and thousands of frogs in the trees, and they were all mating. They were everywhere. Mating frog pairs were falling on me.

As the light came up, I started to grasp the scene. All of the frogs were hopping and green and mating. It was amazing. Everything seemed to be vibrating.

What was your worst experience in the field covering this story?

It was tough hanging around week after week waiting for the first big rain. We waited for about 20 days. I took pictures of this and that, but I really wanted that one picture of a mass mating. That didn't happen until the day after I was supposed to leave.

What was your quirkiest experience in the field covering this story?

I wanted to photograph the blue-sided leaf frog, which is very rare now. It has really declined in the last two decades because a lot of its habitat has been converted into coffee plantations. A scientist told me about a mating population in a pond inside the zoo in the Costa Rican capital of San José.

The zoo is in an area of the city that turns into a red-light district after dark. And these frogs come out at night. So my assistant Robert Horan and I walked from our hotel to the zoo—loaded with rubber boots, backpacks, lights, and a tripod—through all these, um, pretty ladies. It was an absurd scene.

A guard at the zoo let us in, and the next thing we knew we were standing in this dirty little pond listening to the frogs, just a few minutes from a bar.